This invention relates to radar processors which determine whether a target moves on or near the ground or in the air; and it is particularly adapted for use in conjunction with monopulse, doppler type radar systems.
In low and medium pulse repetition frequency (PRF) doppler radar systems (sometimes referred to as velocity ambiguous systems), targets having different velocities can produce identical received signal spectrums. For example, for a given such radar system an automobile moving at 50 knots might produce the same doppler signal spectrum as an aircraft traveling at 500 knots. Hence, radar detection of aircraft can be masked by automobile traffic on land or by surface crafts at sea.
Heretofore several techniques have been used to resolve the above described velocity ambiguity problem. For example, one prior method depends on determining the velocity of the target by observing (or tracking) the target from scan to scan. This requires implementation of a track-while-scan function which can be both complex and expensive to mechanize in reliable configurations. Another prior art approach to resolving the velocity ambiguity problem uses PRF sensitivity to determine whether or not the target's radial velocity is large or small and the slower targets are assumed to be ground targets. This latter technique sacrifices detection of airborne moving targets on or near the "beam" (cross-track targets); and by splitting the dwell time (time on target) on independent detections using two PRFs, an excessive amount of transmitter power is required. In either of the two above outlined approaches their implementation is far from simple.